**Abstract**

Sparkling wines elaborated using the traditional method undergo a second fermentation in the bottle. This process involves an aging time in contact with the lees, which enriches the wine in various substances, especially proteins, mannoproteins and polysaccharides, thanks to the autolysis of the yeasts. As a result of this yeast autolysis, sparkling wines benefit from better integration of carbon dioxide and a clear sensory improvement, especially in the case of long aging. This chapter synthetizes the main results that our research group has obtained about the influence of yeasts autolysis on sparkling wines composition and quality during last years, making special emphasis on the capacity of the lees to release proteins and polysaccharides as well as on their capacity to consume oxygen and thus protect the sparkling wines from oxidation.

**Keywords:** sparkling wines, yeast autolysis, proteins, polysaccharides, oxygen consumption

#### **1. Introduction**

In obedience to the European Regulation CE 1493/99 [1], sparkling wines differ from still wines in the level of internal pressure of carbon dioxide that must be higher than three bars. Sparkling wines are classed in the function of the CO2 origin in two main categories: gasified wines when the carbon dioxide is from an exogenous source and natural sparkling wines when it comes from endogenous fermentation.

Gasified wines are produced simply by injecting carbon dioxide until reaching the desired internal pressure. Normally, these gasified wines have no geographical references, are very cheap and have much lower sensory quality than natural sparkling wines. Given their small interest in their sensory point of view they will not be considered in this chapter. In contrast, natural sparkling wines are obtained using a natural fermentation keeping all or a great proportion of the carbon dioxide inside the vessel in which it has been fermented.

There are different elaboration methods of natural sparkling wines depending on the type of vessel (bottle or tank), time of lees contact, the procedure of eliminating the lees, or if they have had one or two alcoholic fermentations. Moreover,

some of these natural sparkling wines are protected by *Appellations d'origine contrôlées* (AOC) such as *Champagne*, *Cava*, *Francia Corta*, *Prosecco*, *Asti*, *Crémant de Borgougne*, etc.… In that case, each AOC determines the elaboration method, authorized varieties and aging time.

Sparkling wines considered as top quality, such as *Champagne*, *Francia Corta* and *Cava*, are mainly produced by the traditional method, also called for Champagne AOC "*méthode champenoise*". The main characteristic of the traditional method is that after a first fermentation to obtain the base wine, a second fermentation, also called "*prise de mousse*", is performed inside a closed bottle [2, 3]. This second fermentation inside the bottle, and especially the aging time in contact with the lees, completely transform the sparkling wine composition and represents therefore the main differential factor regardless of other sparkling wines produced using other methods [4–6]. During the time of contact of the wine with the lees, several processes occur (**Figure 1**) that explain why the sparkling wines produced by the traditional method generally have higher quality and complexity and are much better considered by the consumers.

Briefly, once the second fermentation is completed, yeast autolysis begins [7]. Autolysis consists of the degradation process of yeast cell structures [8]. Autolysis involves the participation of hydrolytic enzymes, which, by degrading cell structures, cause the release of many substances such as amino acids, peptides, lipids, proteins, nucleotides, proteins, mannoproteins and polysaccharides [9–15]. The release of peptides, proteins, mannoproteins and polysaccharides favors the integration of carbon dioxide, which improves the perception of effervescence in the palate and increases the foam stability [6, 16]. Mannoproteins and polysaccharides also play a positive sensory role by improving mouthfeel [17], whereas some peptides and proteins can contribute to wine sweetness [18]. Some amino acids, peptides and nucleotides are also reported to participate in the umami taste [19] and to be flavor enhancers. Finally, amino acids and lipids have been described as aroma precursors [20] that contribute to the aromatic complexity of sparkling wines.

It has been also reported that yeast lees exert antioxidant activity [21] and recently it has been demonstrated the ability of the lees to consume oxygen [22]. The mechanism by which the lees consume oxygen is not clear but it could be related to the oxidation of membrane lipids [23] or with their content in glutathione [24]. Regardless of the mechanism by which lees consume oxygen, it is clear that their presence slows down the oxidative evolution of the wine by consuming the oxygen that permeates the crown cap. This oxygen consumption by lees is probably the main reason why sparkling wines can usually age for a longer time than still white wines.

In synthesis, yeast autolysis completely modifies the composition of the sparkling wine and therefore also its sensory quality. For all these reasons, the most important AOC (Appellation d'Origine Contrôlée) for sparkling wines has established minimum

**Figure 1.** *Influence of the lees on sparkling wine composition.*

*New Insights about the Influence of Yeasts Autolysis on Sparkling Wines Composition and Quality DOI: http://dx.doi.org/10.5772/intechopen.101314*

ageing times to ensure that autolysis exerts an effect on their composition and quality. For the AOC Cava, the minimum ageing time is 9 months, though its premium sparkling wines are usually aged for longer. The AOC Cava contains two other categories of sparkling wines with extended ageing times. These are the Reserva and Gran Reserva, whose minimum ageing times are 15 and 30 months, respectively. Certain prestigious wineries produce Cavas with an even longer ageing time.

It appears, therefore, that autolysis favors the quality of sparkling wines, at least during the first few years. However, other phenomena take place in parallel—such as aromatic and color oxidation or an excessive lees flavor—which can damage the sensory qualities of these wines [22]. Therefore, we can ask ourselves until what time of aging the quality of the product is favored.

The chapter aims is to synthesize the main results that our research group has obtained on the influence of yeast autolysis on the composition and quality of sparkling wines. This study was carried out studying nine consecutive vintages and was developed in the PhD thesis of Pere Pons entitled "Yeasts autolysis on the manufacture of sparkling wines; influence of aging time on the release of polysaccharides and proteins and the consumption of oxygen by the lees" [25] that was part of the projects GLOBALVITI (global solution to improve wine production against climate change based on robotics, IT technology and biotechnological strategies and vineyard management) and CAVAWINNER (Study and Technological Improvement of the Traditional Processes for the Production of Cava) funded by the Spanish Centre for the Development of Industrial Technology (CDTI - CIEN program). To our knowledge, this is the longest time ever studied about sparkling wines from the AOC Cava.
